Astrocytes, also known as astroglia, are characteristic star-shaped cells in the brain. Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, sometimes called the building blocks of life. ... In the anatomy of animals, the brain, or encephalon, is the supervisory center of the nervous system. ...

Description

Astrocytes are sub-type of the glial cells in the brain. They are also known as astrocytic glial cells. Star-shaped, their many arms span all around neurons. They are the biggest cells found in brain tissue and outnumber ten-fold the neurons. Neuroglia cells of the brain shown by Golgis method. ... Neurons (also spelled neurones or called nerve cells) are the primary cells of the nervous system. ...

Functions

A commonly accepted function is to structure physically the brain. A second function is to provides neurons with food such as glucose.

Apparently, they make a second cell network within the brain. Previously in medical science, the neuronal network was considered the only important one, and astrocytes were looked upon as gap fillers. But recently they have been reconsidered. It appears they can actually control communication between neurons by modifying neurotransmitters dispersion. They modify ability for neurotransmitters to go through synapses by isolating the gap or withdrawing from it. This is known as isolation role. Subsequently signal propagation is changed. Neurotransmitters are chemicals that are used to relay, amplify and modulate electrical signals between two neurons: the presynaptic neuron and the postsynaptic neuron. ... Synapses allow nerve cells to communicate with one another through axons and dendrites, converting electrical signals into chemical ones. ...

Glial cells can communicate independently of the neuronal network. Information moves considerably (100000 times?) slower in the astrocyte network than in the neuronal network, though it could actually complement the fast neuronal information. New exciting perspectives or explanations come with this reconsideration.

Classification

• Type I: Those astrocytes are in direct contact with blood capillaries through astrocytique pod. They are actively helping neuronal metabolism and glucose delivery.
• Type II: Type II atrocytes surrounds neurones and synaptic gap. This coverage varies from 1 to 100%.

Pictures

A (copyrighted) picture of astrocyte next to a neuron (http://www.denniskunkel.com/PublicHtml/Details_PopUp.asp?File_Name=92751A).